Device for measuring micro-linear birefringence through photoelastic modulation and electro-optical modulation cascading

Abstract

The invention relates to the technical field of linear birefringence measurement, in particular to a device for measuring micro-linear birefringence through photoelastic modulation and electro-optical modulation cascading. The device is high in speed, precision and sensitivity, convenient to operate, controllable, high in stability and low in cost. Detection laser light is collimated, then passes through a polarizer, a photoelastic modulator, a sample to be measured and an electro-optical modulator in sequence, and finally is output and irradiated on a photoelectric detector after polarization detection is conducted, signal detection is conducted, a direct-current item is obtained through lowpass filtering, photoelastic modulation fundamental-frequency item data are obtained through FPGA digital phase locking, direct-current item data are transmitted to a computer together with the fundamental-frequency item data, and finally linear birefringence data processing, storage and display are achieved through the computer. The device is mainly applied to photoelastic polarization modulation, the amplitude and direction of linear birefringence can be obtained at the same time, mechanical adjustment is not needed, working is stable, industrialized integration is facilitated, and a new theory and a new method are provided for linear birefringence measurement and relevant application fields.

Description

technical field [0001] The present invention relates to the technical field of linear birefringence measurement, more specifically, to a device for cascade measuring micro linear birefringence by elastic-optic modulation and electro-optic modulation, which is a real-time, stable, high-precision and high-sensitivity micro linear Birefringence measurement device. Background technique [0002] Birefringence is an inherent property of anisotropic optical materials, but isotropic optical materials, such as optical glass, calcium fluoride, and zinc selenide, will also undergo birefringence under the action of external force or processing residual stress. Such birefringence The refraction is so slight that it is often called linear birefringence. But its precise measurement not only provides a detailed understanding of the elastic properties of materials, but also monitors optical inhomogeneities caused by optical components during processing, assembly and fixing. Especially in r...

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Problems solved by technology

The single-elastic optical single-detection system can measure the birefringence of an optical sample with a known fast axis direction at one time. If the fast axis direction is unknown, it is necessary to rotate the sample or the analyzer to obtain the sample amplitude and fast axis direction through two measurements; The single-elastic-light dual-detection system can simultaneously measure the birefringence amplitude and the fast axis direction, but requires two detectors and two lock-in amplifiers, and the polarization direction will change when the detection light path is split to the two detectors by the spectroscopic device , which is difficult to control, thus reducing the accuracy of birefringence detection; the double-elastic optical single-detection system can accurately measure the birefringence amplitude and fast axis direction, but it needs two elastic optical modulators with different modulation frequencies and three lock-in amplifiers to measure The process is complex and expensive

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